Maj.-Gen. Amir Eshel says IDF's military power is 15 times greater than what it had in last conflict with Hezbollah in 2006.

Israel accused Lebanon's Hezbollah guerrillas on Wednesday of putting "thousands" of bases in residential buildings and said it would destroy these in a future conflict, even at the cost of civilian lives.

The unusually explicit threat by air force chief Major-General Amir Eshel appeared to be part of an effort by Israeli officials to prepare world opinion for high civilian casualties in any new confrontation with Hezbollah in Lebanon.

Israel says Iran and Syria have supplied improved missiles to Hezbollah, which fought the technologically superior Israeli military to a standstill in a 2006 war in Lebanon.

"We will have to deal aggressively with thousands of Hezbollah bases which threaten the State of Israel and mainly our interior," Eshel said in a speech, citing Beirut, the Bekaa Valley and southern Lebanon among the locations of the bases.

Other Israeli officials have alleged that Hezbollah uses Lebanese civilian homes as missile silos or gun nests. Eshel said the guerrillas sometimes had entire floors of residential buildings ready, under lock and key, to be used in combat.

"Above and below live civilians whom we have nothing against - a kind of human shield," he told the Fisher Institute for Air and Space Strategic Studies, a think-tank near Tel Aviv.

"And that is where the war will be. That is where we will have to fight in order to stop it and win. Whoever stays in these bases will simply be hit and will risk their lives. And whoever goes out will live."

Israeli Defense Minister Moshe Ya'alon said on Tuesday that Hezbollah now had around 100,000 missiles and rockets, or 30,000 more than figures given in official Israeli assessments in 2013.

Last year, Ya'alon showed UN Secretary-General Ban Ki-moon an Israeli map of alleged Hezbollah positions in southern Lebanese villages, apparently to demonstrate the risk of a high civilian death toll in any new war.

Hezbollah does not comment on its military capabilities but says these have been honed and expanded since the 2006 fighting, in which 1,200 people in Lebanon and 160 Israelis were killed. It says it needs its arms to defend Lebanon from Israeli attack.

Eshel said Israel's military was "dozens" of times more powerful than Hezbollah and had more capabilities than in 2006.

"Our ability today to attack targets on a large scale and with high precision is about 15 times greater than what we did in the (2006) war," he said, saying such intensity was required to keep the fighting short "because the more protracted the war, the more missiles we'll be hit with here".

Much of Hezbollah's attention is now devoted to Syria, where its fighters have been helping President Bashar Assad battle an almost three-year-old insurgency.

While content to watch Hezbollah and the Islamist-led Syrian rebels fight each other, Israel worries that its Lebanese foes will obtain more advanced weaponry from Assad's arsenal.